Circular slide wire resistance element



Nov. 3, 1953 E. A. HAMACHER ET AL 2,653,131

CIRCULAR SLIDE WIRE RESISTANCE ELEMENT "*Filed Nov. 22, 1952 i l/Ill In men rors KURT LOW/ TZSCH EDWARD A. HAMACHER Patented Nov. 3, 1953 CIRCULAR SLIDE WIRE RESISTANCE ELEMENT Edward A. Hamacher, Irvington, and Kurt Lowitzsch, Yonkers, N. Y., assignors to Philips Laboratories, Inc., Irvington-on-Hudson, N. Y.

Application November 22, 1952, Serial N 0. 322,018

6 Claims.

This invention relates to an improved contact brush construction and assembly for a circular or helical slide wire resistance element, and more particularly for the measurement of the resistance between the end of the resistance element and the brush contact when the brush contact is stationary.

Heretofore, the contact brush utilized in a resistance element was continually in engagement with the resistance element and since the contact traversed the resistance element a great number or" times in the course of its use, the resistance element showed excessive and rapid wear result ing in change in resistance values.

A primary object of the present invention is to provide a contact brush construction and assem-- bly which is adapted to be normally disengaged from the resistance element winding yet which may efiectively and rapidly be placed into engagement with the resistance element winding when the roper resistance setting on the resistance element winding is determined. It is apparent, therefore, that since there is only intermittent contact of the contact brush with the resistance element winding, the wear on the winding is considerably reduced necessitating less frequent replacement thereof.

Another object is to provide a rugged and compact helical slide wire contact brush construction and assembly which will operate in a reliable and efficient manner.

The above and other features, objects and advantages of the present invention will be fully understood from the following description considered in connection with the accompanying illustrative drawings, in which is shown a perspective view, partially cut away, of the device embodying the present invention.

Referring more particularly to the drawing, the helical slide wire is secured to the inner wall of cylinder The cylinder is preferably formed from Bakelite or from some other suitable plastic composition. A main drive shaft 6 projects through cylinder :3 and is positioned coaxially to said cylinder. Main drive shaft 6 rtates in either direction by means of a motor coupled thereto (not shown). A sleeve 8 surrounds, and rotates freely about the main drive shaft and. at both ends is provided with a pair of fiat members iii connected together by a tie rod !2. Another pair of relatively flat elements iii are fixed to main drive shaft 6 adjacent to flat members it. A spacer rod it is secured at both its ends to elements it. It is to be noted that since spacer rod 16 is secured to main drive shaft 5, the spacer rod always maintains the same relative position with respect to the main drive shaft.

A contact brush holder 18 composed of insulating material is provided in its upper portion with an aperture 2%) therethrough and two upright guide parts 22!. A contact brush 2% is secured between parts 22 and is adapted to engage h lical slide wire L in a predetermined position of holder it. Contact brush holder i8 is adapted to ride on and traverse spacer rod in since the spacer rod projects through the aperture 23 of holder [8. The lower portion of holder is has a recess 23 which has tie rod i2 positioned therein thereby providing a track for contact brush holdor iii to traverse thereon. A shaft 28 is mounted in drive shaft 5 and has secured to it a transverse pin 30. Pin 39 protrudes through a slot 32 in main drive shaft 8, said slot being positioned parallel to the longitudinal axis of the main drive shaft, and a slot t lcut in sleeve 8 and inclined to the axis of the sleeve.

The operation of the device is as follows: Main drive shaft 6, in this instance, rotates in a clockwise direction and is adapted to be stopped in order to take a resistance reading. The contact brush 24 may be moved manually or mechanically into engagement with helical slide wire 2 by merely moving shaft 28 in the direction of arrow, A. This causes transverse pin 3% to move in slot 32 in a direction parallel to the longitudinal axis of main drive shaft ii. Simultaneously the pin 39 engages inclined slot 3 3. Due to the angle of the slot, sleeve 8 and tie rod 52 rotate in a clock wise direction as indicated by arrow C, thus enabling tie rod l2 to pivot brush holder it on spacer rod it in a counter-clockwise direction as indicated by arrow D. This slight rotation of brush holder it enables the contact brush to engage slide wire 2. It is to be noted that insulated guide parts 22 are located between adjacent windings of the slide wire. t is also apparent that the brush holder is carried along the tie rod l2 and the spacer rod iii in a direction parallel to the longitudinal axis of cylinder 6 upon rotation of sleeve 8. In addition, brush holder It may be rotated about spacer rod it so that the contact brush 24 may disengage the helical slide wire. Brush holder [8 is free to rotate about spacer rod it when shaft 28 is moved in the direction of arrow B thereby causing transverse pin 30 to move in slot 32 thereby engaging inclined slot 34 causing sleeve 8 to rotate in a counter-clockwise direction, thus permitting tie rod i2 to move in a counter-c1ockwise direction in the recess 26 of brush holder it thereby moving contact brush 24 out of engagement with slide wire 2, with a small clearance. The above method of engaging the contact brush and the slide wire by rotating the contact brush holder has the advantage of causing a slight wiping or self-cleaning action in order that good: contact between, the: contact brush andlslidewire isassured. Thisiwiping ac.- tion will not cause excessive wear since the contact brush seldom comes to rest at exactly the same point on the slide wire.

The present device has been used in" conjunc-- tion with an analogue computer of the type in which a helical slide wire is driven by,-means;.of;,

a motor and is automatically; recycled inrsuchia manner that if the contact brushawa'scin continual engagement with the resistance element, the

wear, especially at one end thereof would'be extremely high. It is to be understood thatwe-doi:

not wish to be limited to aconstruction wherein the present device is used with a,computer of the type stated above, but to any structure where a.

variable circular slide wire resistance -may be used effectively.

While we have shown and describedtthepreferred embodiment of our invention, it will be understood that the latter may be embodied otherwise than as herein specificallyillustrated or described and that in-the illustrated-embodiment certain changes in the details of construc-.

tion and in the arrangement of parts may be. made without departing fromthe underlying idea or principle of the invention within the scopeof the appended claims.

What we claim is:

1. A helical slide wire resistance element com-- prising a main drive shaft, a sleeve rotatable about said drive shaft, a pivoting brush contact holder being provided with a brush contact which is adapted to contact said Wire resistance element when said sleeve operatively engages said brush contact holder upon rotation of said sleeve in a predetermined direction and rod, meansiwithin said main drive shaft for coacting with said sleeve to enable said brush contact to engage and disengage said wire resistance element.

2. A helical slide wire resistance element comprising a main drive shaft, a sleeve rotatable about said drive shaft, apivoting brushcontact holder being provided witha brushcontact which when said sleeve is rotated in onedirection and disengage said wire resistance element-- when said sleeve .is rotatedin an oppositedirection, androdr members, anlarcuatebrush contact positioned,

1 is adapted to engage said wire resistance element,

between said guide members and being adapted to contact said wire resistance element when said sleeve operatively engages said brush contact holder upon rotation of said sleeve in a predetermined direction and rod means within said main drive shaft for coacting with said sleeve to enable saidlbrush contact to" engage-and disengage said Wire resistance element;

4. A helical slide wire resistance element comprising a main drive shaft, a sleeve rotatable about said. drive shaft, a pivoting brush contact holder being provided with a brush contact which is adapted to contact said wire resistance element when'saidlsleeve operatively engages said brush contact'holdenupon rotation of said sleeve in a predetermined direction and rod means within saidmain drive shaft, being provided with a pin positioned substantially perpendicular to said rod means and adapted to coact with said sleeve to rotate said sleeve in one direction thereby causingr andengagement of said brushcontact withsaidslidewire resistance element and in another direction thereby causing a disengagement of saidibrush contactwith saidslide wire resistance curing. said. brush contact :holder. to said; main;

drive shaft; a brush contact attached to said brush contact holder which iszadapted. tocontactsaid wire resistance element; when said first rod means engagessaid brush. contact holder upon rotation of said sleeve in a predetermined die recticn, and second rod ineans within saidmain drive shaft for coacting-withzsaidsleeve to enable. said brush contact to engage and disengage said wire resistance element.

6. A helical slidewireresistance element. comprising a main drive shaft, a sleeve rotatablev about said main drive shaft, first rod means, means securing; said first'rcd means parallel to said sleeve and rotatable therewith, second rod means, means securing said second rod means to said main drive shaft and parallel thereto,- a brush contact holder pivoting on saidsecondrod means a brush contact attached tosaid brush contact holder which is adapted to contact said wire resistance element when said first rod means engages said brush contact holder upon rotation of said sleeve in a predetermined direction, and third controlrodmeans within said main drive shaft movable co-axially with said main drive shaft and for coactingwith said sleeve to enable said brush contact to engage and disengage said wire resistance element.-

EDWARD A. HAMACHER. KURT LOWITZSCH.

No references cited. 

